The Competent Person will identify which items of the pressure system fall within the scope of the WSE, such as pressure vessel, protective devices and pipework. Once these items have been established the frequency of examinations will be outlined. The following types of pressurised systems are likely to require a WSE: Compressed air systems where the vessel has a pressure volume product greater than 250 bar litres (This is calculated by multiplying the operating pressure of the vessel in bars by the size of the vessel in litres – bars x litres ) Steam sterilisation autoclaves Coffee machines with steam boilers Rigid vessels over 250 bar litre, this includes expansion vessels and separators Pressure cookers Gas-loaded hydraulic accumulators, if forming part of a pressure system Portable hot water/steam-cleaning unit fitted with a pressure vessel Steam boilers, including standard or narrow-gauge steam locomotives Protective devices such as pressure gauges, safety valves, pipework, level indicators, pressure and temperature switches.